The Greybeards are actualy a refrence to Beowulf. In Beowulf the "Greybeards" were "wise old warriors" for king Hrothgar. I wanted to bring this discusion to light, because I want the WIKI's aproval before making an edit.
The refrence to the "wise old warriors" (Greyberads) is in Beowulf, chapter 23, starting at stanza 1590; This passage states:
"The wise old warriors of Hrothgar,
Like him staring into the monsters' lake,
Saw the waves surging and blood spurting through.
They spoke about Beowulf,
All the greybeards, wispered together
And said that hope was gone."
With this evidence being presented, the Greybeards are undoubtedly a refrence to Beowulf, and not Lord of the Rings.